Block machines are known in the prior art in manifold embodiments. Substantially, in a synchronized process a mould should be provided, a concrete mixture should be filled into the moulding cavities of the mould, the concrete mixture should be packed with a tamper and/or a vibrator, and subsequently the moulded articles should be demoulded. Here, it has been proven successful to insert bolster pallets into the block machine and to lower upwards and downwards open moulds onto the bolster pallets. The concrete mixture is filled from a concrete hopper into a feedbox and let from the feedbox into the mould. Subsequently, the concrete is packed with a vibrator and a tamper pushing onto the concrete. In the next step the tamper and the mould are lifted and the bolster pallet with the moulded articles is taken out of the block machine.
With block machines various moulded stones can be produced. These can in particular differ also in height. So, for example concrete slabs are ca. 30 mm in height, whereas curbstones are ca. 300 mm in height. To be able to produce stones in different heights the block machine must be adjustable. Conventional block machines have a main frame with a vertically adjustable subframe arranged in its interior. Typically, for the vertical adjustment spindle drives are provided. These can be rotated to the desired height manually or with electric motors.
It has been shown that the spindle drive enables a very good adjustment. However, as a drawback it is considered that the adjustment of the height is associated with high expenditure of work, because after a vertical adjustment the subframe must be adjusted in the main frame with high effort. Moreover, the vertical adjustment with spindle drives is slow.